Problem: You are given a directed graph of n vertices and m edges. Vertices are numbered from 1 to n. There is a token in vertex 1.

The following actions are allowed: 

  * Token movement. To move the token from vertex u to vertex v if there is an edge u → v in the graph. This action takes 1 second. 
  * Graph transposition. To transpose all the edges in the graph: replace each edge u → v by an edge v → u. This action takes increasingly more time: k-th transposition takes 2^{k-1} seconds, i.e. the first transposition takes 1 second, the second one takes 2 seconds, the third one takes 4 seconds, and so on. 



The goal is to move the token from vertex 1 to vertex n in the shortest possible time. Print this time modulo 998 244 353.

Input

The first line of input contains two integers n, m (1 ≤ n, m ≤ 200 000).

The next m lines contain two integers each: u, v (1 ≤ u, v ≤ n; u ≠ v), which represent the edges of the graph. It is guaranteed that all ordered pairs (u, v) are distinct.

It is guaranteed that it is possible to move the token from vertex 1 to vertex n using the actions above.

Output

Print one integer: the minimum required time modulo 998 244 353.

Examples

Input


4 4
1 2
2 3
3 4
4 1


Output


2


Input


4 3
2 1
2 3
4 3


Output


10

Note

The first example can be solved by transposing the graph and moving the token to vertex 4, taking 2 seconds.

The best way to solve the second example is the following: transpose the graph, move the token to vertex 2, transpose the graph again, move the token to vertex 3, transpose the graph once more and move the token to vertex 4.

Solution (in JAVA):

Solution:
import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.DataInputStream;
import java.io.Flushable;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.util.AbstractCollection;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.Objects;
import java.util.PriorityQueue;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
	static class TaskAdapter implements Runnable {
		@Override
		public void run() {
			long startTime = System.currentTimeMillis();
			InputStream inputStream = System.in;
			OutputStream outputStream = System.out;
			FastReader in = new FastReader(inputStream);
			Output out = new Output(outputStream);
			CGraphTranspositions solver = new CGraphTranspositions();
			solver.solve(1, in, out);
			out.close();
			System.err.println(System.currentTimeMillis()-startTime+"ms");
		}
	}

	public static void main(String[] args) throws Exception {
		Thread thread = new Thread(null, new TaskAdapter(), "", 1<<28);
		thread.start();
		thread.join();
	}

	static class CGraphTranspositions {
		private final int mod = 998244353;

		public CGraphTranspositions() {
		}

		public boolean good(ArrayList<CGraphTranspositions.State> al, CGraphTranspositions.State s) {
			for(CGraphTranspositions.State x: al) {
				if(x.pow<s.pow&&x.compareTo(s)<=0) {
					return false;
				}
			}
			return true;
		}

		public void solve(int kase, InputReader in, Output pw) {
			int n = in.nextInt(), m = in.nextInt();
			ArrayList<Integer>[][] graph = new ArrayList[2][n];
			graph[0] = in.nextDirectedGraph(n, m);
			for(int i = 0; i<n; i++) {
				graph[1][i] = new ArrayList<>();
			}
			for(int i = 0; i<n; i++) {
				for(int j: graph[0][i]) {
					graph[1][j].add(i);
				}
			}
			ArrayList<CGraphTranspositions.State>[][] visited = new ArrayList[n][2];
			for(int i = 0; i<n; i++) {
				for(int j = 0; j<2; j++) {
					visited[i][j] = new ArrayList<>();
				}
			}
			HashSet<Pair<Integer, Integer>> hs = new HashSet<>(n*4);
			PriorityQueue<CGraphTranspositions.State> pq = new PriorityQueue<>(n*4);
			pq.add(new CGraphTranspositions.State(0, 0, 0));
			while(!pq.isEmpty()) {
				CGraphTranspositions.State cur = pq.poll();
				var p = cur.getPair();
				if(hs.contains(p)||!good(visited[cur.ind][cur.pow&1], cur)) {
					continue;
				}
////				Utilities.Debug.dbg(cur);
				hs.add(p);
				visited[cur.ind][cur.pow&1].add(cur);
				if(cur.ind==n-1) {
////					Utilities.Debug.dbg(cur);
					pw.println((Utilities.math.pow(2, cur.pow, mod)+cur.time+mod-1)%mod);
					return;
				}
				CGraphTranspositions.State s = cur.trans();
				if(!hs.contains(s.getPair())&&good(visited[s.ind][s.pow&1], s)) {
					pq.add(s);
				}
				for(int i: graph[cur.pow&1][cur.ind]) {
					s = cur.move(i);
					if(!hs.contains(s.getPair())&&good(visited[s.ind][s.pow&1], s)) {
						pq.add(s);
					}
				}
			}
		}

		static class State implements Comparable<CGraphTranspositions.State> {
			int ind;
			int pow;
			int time;

			public State(int ind, int pow, int time) {
				this.ind = ind;
				this.pow = pow;
				this.time = time;
			}

			public CGraphTranspositions.State move(int next) {
				return new CGraphTranspositions.State(next, pow, time+1);
			}

			public CGraphTranspositions.State trans() {
				return new CGraphTranspositions.State(ind, pow+1, time);
			}

			public Pair<Integer, Integer> getPair() {
				return new Pair<>(ind, pow);
			}

			public int compareTo(CGraphTranspositions.State s) {
				if(s.pow==pow) {
					return Integer.compare(time, s.time);
				}else if(Math.max(s.pow, pow)<=60) {
					return Long.compare((1L<<pow)+time, (1L<<s.pow)+s.time);
				}
				return Integer.compare(pow, s.pow);
			}

			public String toString() {
				return "State{"+
						"ind="+ind+
						", pow="+pow+
						", time="+time+
						'}';
			}

		}

	}

	static class Utilities {
		public static class Debug {
			public static final boolean LOCAL = System.getProperty("ONLINE_JUDGE")==null;

			private static <T> String ts(T t) {
				if(t==null) {
					return "null";
				}
				try {
					return ts((Iterable) t);
				}catch(ClassCastException e) {
					if(t instanceof int[]) {
						String s = Arrays.toString((int[]) t);
						return "{"+s.substring(1, s.length()-1)+"}";
					}else if(t instanceof long[]) {
						String s = Arrays.toString((long[]) t);
						return "{"+s.substring(1, s.length()-1)+"}";
					}else if(t instanceof char[]) {
						String s = Arrays.toString((char[]) t);
						return "{"+s.substring(1, s.length()-1)+"}";
					}else if(t instanceof double[]) {
						String s = Arrays.toString((double[]) t);
						return "{"+s.substring(1, s.length()-1)+"}";
					}else if(t instanceof boolean[]) {
						String s = Arrays.toString((boolean[]) t);
						return "{"+s.substring(1, s.length()-1)+"}";
					}
					try {
						return ts((Object[]) t);
					}catch(ClassCastException e1) {
						return t.toString();
					}
				}
			}

			private static <T> String ts(T[] arr) {
				StringBuilder ret = new StringBuilder();
				ret.append("{");
				boolean first = true;
				for(T t: arr) {
					if(!first) {
						ret.append(", ");
					}
					first = false;
					ret.append(ts(t));
				}
				ret.append("}");
				return ret.toString();
			}

			private static <T> String ts(Iterable<T> iter) {
				StringBuilder ret = new StringBuilder();
				ret.append("{");
				boolean first = true;
				for(T t: iter) {
					if(!first) {
						ret.append(", ");
					}
					first = false;
					ret.append(ts(t));
				}
				ret.append("}");
				return ret.toString();
			}

			public static void dbg(Object... o) {
				if(LOCAL) {
					System.err.print("Line #"+Thread.currentThread().getStackTrace()[2].getLineNumber()+": [");
					for(int i = 0; i<o.length; i++) {
						if(i!=0) {
							System.err.print(", ");
						}
						System.err.print(ts(o[i]));
					}
					System.err.println("]");
				}
			}

		}

		public static class math {
			public static long pow(long base, long exp, long mod) {
				long ans = 1, cur = base;
				while(exp>0) {
					if((exp&1)>0) {
						ans = (ans*cur)%mod;
					}
					cur = (cur*cur)%mod;
					exp >>= 1;
				}
				return ans;
			}

		}

	}

	static class Output implements Closeable, Flushable {
		public StringBuilder sb;
		public OutputStream os;
		public int BUFFER_SIZE;
		public String lineSeparator;

		public Output(OutputStream os) {
			this(os, 1<<16);
		}

		public Output(OutputStream os, int bs) {
			BUFFER_SIZE = bs;
			sb = new StringBuilder(BUFFER_SIZE);
			this.os = new BufferedOutputStream(os, 1<<17);
			lineSeparator = System.lineSeparator();
		}

		public void println(long l) {
			println(String.valueOf(l));
		}

		public void println(String s) {
			sb.append(s);
			println();
		}

		public void println() {
			sb.append(lineSeparator);
		}

		private void flushToBuffer() {
			try {
				os.write(sb.toString().getBytes());
			}catch(IOException e) {
				e.printStackTrace();
			}
			sb = new StringBuilder(BUFFER_SIZE);
		}

		public void flush() {
			try {
				flushToBuffer();
				os.flush();
			}catch(IOException e) {
				e.printStackTrace();
			}
		}

		public void close() {
			flush();
			try {
				os.close();
			}catch(IOException e) {
				e.printStackTrace();
			}
		}

	}

	static interface InputReader {
		int nextInt();

		default ArrayList<Integer>[] nextDirectedGraph(int n, int m) {
			ArrayList<Integer>[] ret = new ArrayList[n];
			for(int i = 0; i<n; i++) {
				ret[i] = new ArrayList<>();
			}
			for(int i = 0; i<m; i++) {
				ret[nextInt()-1].add(nextInt()-1);
			}
			return ret;
		}

	}

	static class FastReader implements InputReader {
		final private int BUFFER_SIZE = 1<<16;
		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer;
		private int bytesRead;

		public FastReader(InputStream is) {
			din = new DataInputStream(is);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public int nextInt() {
			int ret = 0;
			byte c = skipToDigit();
			boolean neg = (c=='-');
			if(neg) {
				c = read();
			}
			do {
				ret = ret*10+c-'0';
			} while((c = read())>='0'&&c<='9');
			if(neg) {
				return -ret;
			}
			return ret;
		}

		private boolean isDigit(byte b) {
			return b>='0'&&b<='9';
		}

		private byte skipToDigit() {
			byte ret;
			while(!isDigit(ret = read())&&ret!='-') ;
			return ret;
		}

		private void fillBuffer() {
			try {
				bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
			}catch(IOException e) {
				e.printStackTrace();
				throw new InputMismatchException();
			}
			if(bytesRead==-1) {
				buffer[0] = -1;
			}
		}

		private byte read() {
			if(bytesRead==-1) {
				throw new InputMismatchException();
			}else if(bufferPointer==bytesRead) {
				fillBuffer();
			}
			return buffer[bufferPointer++];
		}

	}

	static class Pair<T1, T2> implements Comparable<Pair<T1, T2>> {
		public T1 a;
		public T2 b;

		public Pair(Pair<T1, T2> p) {
			this(p.a, p.b);
		}

		public Pair(T1 a, T2 b) {
			this.a = a;
			this.b = b;
		}

		public String toString() {
			return a+" "+b;
		}

		public int hashCode() {
			return Objects.hash(a, b);
		}

		public boolean equals(Object o) {
			if(o instanceof Pair) {
				Pair p = (Pair) o;
				return a.equals(p.a)&&b.equals(p.b);
			}
			return false;
		}

		public int compareTo(Pair<T1, T2> p) {
			int cmp = ((Comparable<T1>) a).compareTo(p.a);
			if(cmp==0) {
				return ((Comparable<T2>) b).compareTo(p.b);
			}
			return cmp;
		}

	}
}